This invention relates to a kind of degradable material, its disposable products and processing method thereof.
Currently, disposable tableware products made of plastic foam and plastics have the following defects:
(1) Large consumption of petroleum resources;
(2) Freon used in the foaming process destroys the ozone layer of atmosphere;
(3) Inability to decay even if buried underground for 200 years, causing serious white pollution, etc.
At present, disposable tableware products substituted by paper or starch materials have the following shortcomings: paper materials consume a large amount of bamboo and wood, thus damaging green resources in addition to causing water pollution by the pulp and paper production process, while substitutes by starch material consume huge quantity of grains, and are susceptible to mildew. Apparently, such substitutes still have technical problems as well as environmental problems that need to be addressed.
Most of the published patents for utilization of shell or stalk of crops as raw materials to make disposable tableware products use wet and cold pressing processes, requiring low temperature heating, long time drying and repeated coating, and, thus, resulting in multiple steps in operation, complicated processes, large amount of investment, high cost of the products, and difficulties in their promotion and popularization. A small portion of the said published patents use dry and hot pressing process, but the organic high molecular polymer used as adhesives is expensive, and some of the adhesives do not meet sanitary standards. Although the processes are simple, but the costs of the products cannot be reduced to a level acceptable in the markets.
In view of the defects and shortcomings of the above-stated processes for producing disposable tableware products by using shell or stalks of crops as raw materials, one object of the present invention is to provide a degradable composite material.
Another object of the present invention is to provide an application of the degradable composite material in manufacturing of disposable tableware.
The further object of the present invention is to provide a molding process method using the degradable composite material in the manufacturing of disposable tableware.
The degradable composite material of the invention comprises the following components by weight and in parts:
plant fiber: 60-90 parts
urea-formaldehyde resin 10-35 parts
melamine resin 3-10 parts
food coloring agent 1-10 parts
wherein the molecular weight of the urea-formaldehyde resin is 300-600.
The plant fiber used in this invention is crop hull or stalk and its amount is preferably in the range of 70 to 80 parts by weight.
In this invention, the molecular weight of the urea formaldehyde resin is 300-600, preferably 300-400. The urea-formaldehyde resin does not contain fluorescent brightening agent or sizing. The urea-formaldehyde resin can be prepared by the following method:
1. Formulation (by weight and in parts):
urea 80-100 parts
formaldehyde (37%) 160-240 parts
sodium dibutylnaphthalenesulfonate 5-10 parts
Resorcin 2.5-7.5 parts
Glycerol 16-24 parts pH value conditioner appropriate amount
2. Preparation Method:
(1) According to the weight parts mentioned above, add urea, formaldehyde (37%) and glycerol into a reaction vessel with an agitator and stir them at a 60xc2x0 C. until the urea is fully dissolved to form a first mixed solution. Cool the first mixed solution to 20-25xc2x0 C. and add sodium diphenylnaphthalenesulfonate and Resorcin according to the said weight parts. Then stir above mixture for about 10-60 minutes at a rotation speed of 120 rpm to form a second mixed solution.
(2) Adjust the pH value of the second mixed solution to 7-8 with a pH value conditioner, then stir it for 30 minutes at a rotate speed of 180-260 rpm, and stir it for another 30 minutes at a rotate speed of 300-400 rpm to form a third mixed solution. Then pour the third mixed solution into a storage and dry it in the dark for 24 hours to obtain an urea formaldehyde resin base material. Warm and dry the urea-formaldehyde resin base material for 6 hours at 60xc2x0 C., and then retain the final urea formaldehyde resin for later use.
The pH value conditioner utilized is either oxalic acid, acetic acid or phosphoric acid, preferably oxalic acid.
The amount of the melamine is preferably in the range of 3 to 5 parts by weight.
The food coloring agent of the invention is selected from the group consisting of titanium white, zinc oxide, iron oxide red, pigment yellow 147, pigment blue 15, and combinations thereof. Preferably, it is titanium white. The amount of the food coloring agent is in the range of 3 to 5 parts by weight.
The processing method for manufacturing tableware product using the degradable composite material of the invention comprises the following steps:
(1) pulverize the plant shell or stalk of crops into 60 mesh or over, and then mix the pulverized shell or stalk of crops with urea-formaldehyde resin and melamine resin proportionately and thoroughly to form a mixture of the biodegradable composite material;
(2) feed the mixture of the biodegradable composite material into the concave molding mould positioned in a pushing upward type oil hydraulic press in a fixed quantity and position with temperature of the mould maintained at 125-190xc2x0 C.;
(3) control the pressure of the oil hydraulic press at between 10-30 Mpa and keep the press operating at 3 intervals by maintaining at above pressure for 3-30 seconds per each interval, so as to obtain the finished products.
Preferably, the grinder is a turbine grinder, and maintain the concave mould temperature at 160xc2x0 C., the convex mould temperature at 170xc2x0 C., working pressure at 25 Mpa, keep the press operating at 3 intervals by maintaining at above pressure for 3 seconds per each interval.
The invention will be better understood on reading the following detailed description of non-limiting embodiments of the invention.